1. Field of the Invention
The present invention relates to conveyor for transporting people, such as escalators, moving sidewalk, etc.
2. Description of the Related Art
As a conventional example of the conveyor of this type, an escalator with a handrail drive unit of a winding drive type is disclosed in Published Examined Japanese Patent Application No. 61-29314. According to this system, one relatively large handrail driving wheel is rotated in association with a treadboard drive section for driving a large number of treadboards, and a moving handrail, which is wound half round the driving wheel, is driven by the resulting force of rolling friction.
Meanwhile, there is a social demand for efficient use of the floor space of buildings. To meet this demand, the effective area of the buildings must be increased by minimizing the installation space for escalators. As is also described in the aforesaid patent application, therefore, handrail drive units of a straight drive type have started to be widely used. This system, unlike the winding drive system, permits reduction in both width and depth of the escalators. According to the straight drive system, a handrail is vertically held between a plurality of rollers, which are rotated in association with a treadboard drive section so that the handrail is driven frictionally.
In either of these two drive systems, a heavy load sometimes may act on the moving handrail while it is traveling, thereby changing the traveling speed of the handrail. In such a case, the treadboards and the moving handrail, which originally are expected to move in synchronism and at the same speed with one another, cease to be synchronous, so that users or passengers cannot keep their balance on the treadboards, exposing themselves to danger.
Thus, in the conventional conveyor, as described in Published Unexamined Japanese Patent Application No. 63-143191, for example, the traveling speed of the moving handrail and the driving speed of the treadboard drive section are detected individually, and the change of the handrail speed is detected by comparing the two speeds. If the change of the handrail speed is detected in this manner, that is, if there is a difference between the detected speeds, an alarm is given or the drive of the escalator is stopped for safety's sake.
In the conveyor described above, however, a sensor for detecting the traveling speed of the moving handrail and a sensor for detecting the driving speed of the treadboard drive section are provided independently of each other in separate positions. Accordingly, the sensor means requires a wide setting space, and the mounting work, maintenance, and inspection for the sensor means are time-consuming.